0x19. C - Stacks, Queues - LIFO, FIFO

The Monty language

Monty 0.98 is a scripting language that is first compiled into Monty byte codes (Just like Python). It relies on a unique stack, with specific instructions to manipulate it. The goal of this project is to create an interpreter for Monty ByteCodes files.

The monty program

Usage: monty file:

./monty bytecode.m

where file is the path to the file containing Monty byte code
If the user does not give any file or more than one argument to your program, print the error message USAGE: monty file, followed by a new line, and exit with the status EXIT_FAILURE
If, for any reason, its not possible to open the file, print the error message Error: Can't open file <file>, followed by a new line, and exit with the status EXIT_FAILURE
- where <file> is the name of the file
If the file contains an invalid instruction, print the error message L<line_number>: unknown instruction <opcode>, followed by a new line, and exit with the status EXIT_FAILURE
- where <line_number>is the line number where the instruction appears.
- Line numbers always start at 1
The monty program runs the bytecodes line by line and stop if either:
- it executed properly every line of the file
- it finds an error in the file
- an error occured
If you cant malloc anymore, print the error message Error: malloc failed, followed by a new line, and exit with status EXIT_FAILURE
You have to use malloc and free and are not allowed to use any other function from man malloc (realloc, calloc, )

Example of bytecode

There is not more than one instruction per line. There can be any number of spaces before or after the opcode and its argument

$ cat -e bytecodes/000.m
push 0$
push 1$
push 2$
  push 3$
                   pall    $
push 4$
    push 5    $
      push    6        $
pall$
$

Monty byte code files can contain blank lines (empty or made of spaces only, and any additional text after the opcode or its required argument is not taken into account

$ cat -e bytecodes/001.m
push 0 Push 0 onto the stack$
push 1 Push 1 onto the stack$
$
push 2$
  push 3$
                   pall    $
$
$
                           $
push 4$
$
    push 5    $
      push    6        $
$
pall This is the end of our program. Monty is awesome!$
$

Usage

The code is compiled this way:

$ gcc -Wall -Werror -Wextra -pedantic *.c -o monty

Any output is printed on stdout
Any error message is printed on stderr

Operation codes :

Opcode	Description
push	Pushes an element to the stack
pall	Prints all the values on the stack, starting from the top of the stack
pint	Prints the value at the top of the stack
pop	Removes the top element of the stack
swap	Swaps the top two elements of the stack
add	Adds the top two elements of the stack
sub	Subtracts the top element of the stack from the second top element of the stack
mul	Multiplies the second top element of the stack with the top element of the stack
div	Divides the second top element of the stack by the top element of the stack
mod	Computes the rest of the division of the second top element of the stack by the top element of the stack
pchar	Prints the char at the top of the stack, followed by a new line
pstr	Prints the string starting at the top of the stack, followed by a new line
rotr	Rotates the stack to the bottom
rotl	Rotates the stack to the top
nop	Doesnt do anything
stack	(Default) LIFO
queue	Set to FIFO

Learning Objectives

What do LIFO and FIFO mean
What is a stack, and when to use it
What is a queue, and when to use it
What are the common implementations of stacks and queues
What are the most common use cases of stacks and queues
What is the proper way to use global variables